Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$81.87	4.368%	$85.4461	$85.45	$85.45	$85.40
Purchase #2	$205.49	11.737%	$229.6084	$229.61	$229.60	$229.60
Purchase #3	$121.59	13.260%	$137.7128	$137.71	$137.70	$137.70
Purchase #4	$9.71	12.165%	$10.8912	$10.89	$10.90	$10.90
Purchase #5	$246.49	10.315%	$271.9154	$271.92	$271.90	$271.90
Purchase #6	$102.44	4.400%	$106.9474	$106.95	$106.95	$106.90
Purchase #7	$80.68	12.237%	$90.5528	$90.55	$90.55	$90.60
7 purchase totals =	$848.27		$933.0741	$933.08	$933.05	$933.00